Why do I look skinnier in the morning than in the afternoon?

Anonymous
When I look in the bathroom mirror in the morning my stomach is flat and I look skinny. In the afternoon, my stomach is not flat any more. Even if I fast during the morning, by lunch I still look fatter than I did when I had just woken up. Why is this? How can I maintain what I look like in the morning throughout the day?
Updates
+1 y
It cannot be food/dehydration, as if I don't eat or drink anything until 1 pm, I still look fatter than I did at 7am. I read online that you are taller in the morning but only like 5 mm and I find it strange that 5 mm can cause such a big difference
Why do I look skinnier in the morning than in the afternoon?
7 Opinion